A copper clad laminate used for a conventional printed circuit board is prepared by impregnating a base material of a glass fabric into a varnish of the thermosetting resin and semi-curing it to make a prepreg, and then heating and pressing it together with a copper foil. The prepreg is used again for constructing a circuit pattern on such copper foil laminate and again building-up thereon.
However, as electronic equipment becomes thinner and lighter, a phenomenon where the package becomes warped is generated due to the thinness and the high density of the semiconductor package.
Such warpage phenomenon is exacerbated by a phenomenon in which the sub-substrate itself is not restored while repeating high temperatures in the PCB reflow process. Therefore, due to the above-mentioned problem, there is a demand for a product having a low hardening shrinkage ratio and securing the flowability even if it is processed at a high temperature.
However, thermosetting resin compositions suitable for the PCB reflow process have not yet been developed.